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61.
Ashok V. Bankar Ameeta R. Kumar Smita S. Zinjarde 《Applied microbiology and biotechnology》2009,84(5):847-865
Yarrowia lipolytica is a fungus that degrades hydrophobic substrates very efficiently. The fungus displays several important characteristics
that have encouraged researchers to study various basic biological and biotechnological applications in detail. Although the
organism has been used as model system for studying dimorphism, salt tolerance, heterologous protein expression, and lipid
accumulation, there are no recent reviews on the environmental and industrial applications of this organism. Included here
are applications in bioremediation of environments contaminated with aliphatic and aromatic compounds, organic pollutants,
2,4,6-trinitrotoluene, and metals. A variety of industrially important recent processes for the synthesis of β-hydroxy butyrate,
l-dopa, and emulsifiers have also been reviewed. Production of unique inherent enzymes (inulinases, α-mannosidases), novel
applications of esterases and lipases, and the use of the fungus for heterologous expression of biotechnologically relevant
products have also been highlighted. The review while entailing a general overview focuses critically on some of the recent
advances on the applications of this yeast. The examples cited here demonstrate the use of wild-type, mutant as well as genetically
manipulated strains of Y. lipolytica for the development of different products, processes, and technologies. This also throws light on how a single organism can
be versatile with respect to its metabolic abilities and how it can be exploited for a variety of purposes. This review will
thus form a base for future developments in this field. 相似文献
62.
Lactobacillus salivarius cells contain an inducible transport system for folate. Influx via this system is time- and temperature-dependent, requires glucose and glutamine for optimum activity, and is half-maximal at folate concentrations in the nanomolar range. The folate internalized after 30 min at 30 degrees C is not released from the cells by excess extracellular folate and is recovered in cell extracts primarily in metabolized forms. A membrane-associated folate-binding protein is also present in cells that have been induced to transport folate. This binding protein constitutes 1% of total cellular protein, exhibits a high affinity for folate (KD = 0.40 nM), and requires divalent cations for optimum binding activity. Folate binds rapidly to this protein, while the exchange of bound substrate with folate added subsequently is relatively slow and dependent on the metabolic state of the cell. The transport rate per binding site is 0.05/min at 30 degrees C. A comparison of substrate specificity showed that folate binding and transport are both inhibited to the same extent by several different folate compounds, and a parallel irreversible inhibition of both processes is observed by prior treatment of the cells with a carbodiimide-activated derivative of folic acid. Binding protein labeled covalently with [3H]folate and solubilized with Triton X-100 was purified by a fractionation procedure involving absorption and elution from microgranular silica and molecular sieve chromatography. The isolated protein appeared homogeneous by gel electrophoresis and had an apparent molecular weight of 21,000. Monoclonal antibodies to the folate transport protein of Lactobacillus casei showed a high degree of cross-reactivity to the isolated binding protein from L. salivarius, indicating that these proteins share common epitopes. These results suggest that folate uptake by L. salivarius proceeds via an abundant membrane-associated binding protein which facilitates the movement of folate across the membrane as an electroneutral complex with cations. The substrate then slowly dissociates from internalized binding sites and is metabolized sequentially to coenzyme forms and then to membrane-impermeable folylpolyglutamates. 相似文献
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64.
Dipnarayan Saha Vajinder Kumar Shripad Ramachandra Bhat Ramamurthy Srinivasan 《Plant Molecular Biology Reporter》2011,29(2):265-277
Isolation and characterization of promoters are important in understanding gene regulation and genetic engineering of crop
plants. Earlier, a pentatricopeptide repeat protein (PPR) encoding gene (At2g39230), designated as Lateral Organ Junction (LOJ) gene, was identified through T-DNA promoter trapping in Arabidopsis thaliana. The upstream sequence of the LOJ gene conferred on the reporter gene a novel LOJ-specific expression. The present study was aimed at identifying and characterizing
the cis-regulatory motifs responsible for tissue-specific expression in the −673 and +90 bases upstream of the LOJ gene recognized as LOJ promoter. In silico analysis of the LOJ promoter revealed the presence of a few relevant regulatory motifs and a unique feature like AT-rich inverted repeat. Deletion
analysis of the LOJ promoter confirmed the presence of an enhancer-like element in the distal region (−673/−214), which stimulates a minimal
promoter-like sequence in the −424/−214 region in a position and orientation autonomous manner. The −136/+90 region of the
LOJ promoter was efficient in driving reporter gene expression in tissues like developing anthers and seeds of Arabidopsis. A positive regulation for the seed- and anther-specific expression module was contemplated within the 5′ untranslated region
of the LOJ gene. However, this function was repressed in the native context by the lateral organ junction-specific expression. The present
study has led to the identification of a novel lateral organ junction-specific element and an enhancer sequence in Arabidopsis with potential applications in plant genetic engineering. 相似文献
65.
Experimental evidence suggests that proteins adsorbed to hydrophobic surfaces at low coverages are stabilized relative to the bulk. For larger coverages, proteins unfold and form β-sheets. We performed computer simulations on model proteins and found that: 1), For weakly adsorbing surfaces, unfolded conformations lose more entropy upon adsorption than folded ones. 2), The melting temperature, both in the bulk and at surfaces, decreases with increasing protein concentration because of favorable interprotein interactions. 3), Proteins in the bulk show large unfolding free energy barriers; this barrier decreases at stronger adsorbing surfaces. We conjecture that typical experimental temperatures appear to be below the bulk melting temperature for a single protein, but above the melting temperature for concentrated protein solutions. Purely thermodynamic factors then explain protein stabilization on adsorption at low concentrations. However, both thermodynamic and kinetic factors are important at higher concentrations. Thus, proteins in the bulk do not denature with increasing concentration due to large kinetic barriers, even though the aggregated state is thermodynamically preferred. However, they readily unfold upon adsorption, with the surface acting as a heterogeneous catalyst. The thermal behavior of proteins adsorbed to hydrophobic surfaces thus appears to follow behavior independent of their chemical specificity. 相似文献
66.
Ramesh Gannu Chinna Reddy Palem Shravan Kumar Yamsani Vamshi Vishnu Yamsani Madhusudan Rao Yamsani 《AAPS PharmSciTech》2010,11(2):976-985
The purpose of the present study was to develop and optimize reservoir-based transdermal therapeutic system (TTS) for buspirone
(BUSP), a low bioavailable drug. A three-factor, three-level Box–Behnken design was employed to optimize the TTS. Hydroxypropyl
methylcellulose, d-limonene and propylene glycol were varied as independent variables; cumulative amount permeated across rat abdominal skin
in 24 h, flux and lag time were selected as dependent variables. Mathematical equations and response surface plots were used
to relate the dependent and independent variables. The statistical validity of polynomials was established, and optimized
formulation factors were selected by feasibility and grid search. Validation of the optimization study with seven confirmatory
runs indicated high degree of prognostic ability of response surface methodology. BUSP-OPT (optimized formulation) showed
a flux 104.6 μg cm−2 h−1, which could meet target flux. The bioavailability studies in rabbits showed that about 2.65 times improvement (p < 0.05) in bioavailability, after transdermal administration of BUSP-OPT compared to oral solution. The ex vivo–in vivo correlation was found to have biphasic pattern and followed type A correlation. Reservoir-based TTS for BUSP was developed
and optimized using Box–Behnken statistical design and could provide an effective treatment in the management of anxiety. 相似文献
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